Naphtha reforming with noble metal catalyst



3,089,845 NAPHTHA. REEGRMKNG WHTH NUBLE METAL CATALYST Robert E. Mosely, Waiuut Creek, Caiif, assignor to Shell Oil Qompany, New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 27, 1%0, Ser- No. 78,253 17 Claims. (Cl. 208-139) This invention relates to the catalytic reforming of naphth-as and fractions thereof with a special noble metal-containing catalyst.

Catalytic reforming is a well known and now Widely used process for upgrading hydrocarbon fractions boiling in the motor gasoline or naphtha boiling range to increase their actone numbers. In this process a selected naphtha fraction is separated and passed in the vapor phase along with about 3 to mols of hydrogen per mol of oil at a pressure of about 50 to 1000 p.s.i.g. and generally between about 200 and 700 p.s.i.g. to one or more reaction zones containing a dehydrogenation catalyst. The usual catalyst comprises a minor amount, e.-g. 0.1 to 2% of a noble metal, e.g. platinum, palladium and rhodium, supported on a suitable carrier such as alumina, alumina silica composites and the like and frequently promoted with minor amounts, e.g. 0.1 to 5%, of chlorine and/ or fluorine.

In the reforming process many reactions, both primary and secondary, take place. The chief reaction is the dehydrogenation of naphthenic hydrocarbons to the corresponding aromatic hydrocarbons. Other important reactions are the isomerization of paraiiins, dehydrocyclization of paraffins to aromatics, and the more or less selective cracking of low octane number high molecular weight paraffins.

Catalytic reforming generally has been applied to relatively heavy naphthas, i.e. those having a boiling range of about 200 F. to 420 F., since these fractions are more susceptible to octane improvement because of their rich naphthenic content, e.g. about 40% or more. The lower boiling naphtha fractions, such as hexane fractions which contain only about naphthenes, are less susceptible to octane improvement. However, in view of the continuing demand for high octane number gasolines, it has become necessary to reform light naphtha fractions and to operate at much higher severities where the dehydrocyclization and hydrocracking reactions become more important.

The severity of the reforming operation is a function of the temperature, pressure, hydrogen to hydrocarbon ratio and space velocity. It increases with increasing temperature and decreasing pressure, hydrogen to hydrocarbon ratio and space velocity. At mild severity conditions, i.e. to produce a product of, say, 95 F-1-3 octane number, the various reactions are obtained to different extents than when reforming under severe conditions to produce a product having an F-l0 octane number of 100 or above. Thus, one catalyst may give best results under the former conditions while a different catalyst may give best results under the latter conditions.

t is to be noted that the usual noble metal reforming catalysts, such as the platinum type of catalyst, are all essentially equivalent in being capable of producing a product of the desired octane number. They difier, however, in the temperatures required to achieve a given octane number with any particular feed and, more im portantly, they differ in the amount of loss sustained in achieving that octane number. As the reforming severity is increased, the loss is increased at an accelerated rate. For instance, in the case of reforming a typical naphtha with a conventional well known and widely used platinum reforming catalyst, the loss when reforming to F-1-0 octane number amounts to about 15% by volume, whereas When reforming to Fl0 octane number the loss amounts to about 20% by volume. That is, for every 100 barrels of naphtha feed the refiner obtains only about 80 barrels of debutanized gasoline. Thus, it will be noted that to achieve the extra 5 octane numbers the amount of the loss is increased by 5 barrels per 100 barrels of feed. It is, therefore, of the utmost importance to main tain the losses as low as possible.

The increased loss in yield as reforming severity is increased is due primarily to reaction of the paraffins, such as dehydrocyclization and hydrocracking reactions. In dehydrocyclization, most of the loss in yield is associated with the density shift in going from a paraffin to an aromatic. For example, for the conversion of normal hexane to benzene the theoretical yield on a volumetric basis is about 68%, and for the conversion of octanes to a mixture of xylene and ethylbenzene the theoretical yield is 75-76%. In the hydrocracking reaction the loss is primarily due to conversion to hydrocarbons boiling below the gasoline boiling range. The former reaction is preferred.

Therefore, it is an object of this invention to provide an improved catalyst which is active in the reforming of naphthas to high yields of products boiling within the gasoline boiling range.

It has now been found that catalysts for the reforming of naphtha fractions can be improved by treating the support material with an alkyl silicate. The reasons for the improved activity resulting from the treatment have not been explained. But, as will be shown by examples which follow, activity and selectivity of the catalyst are markedly increased.

The alkyl orthosilicates, sometimes called the organic esters of silicon, are well known and are represented by the formula R SiO' wherein R designates an alkyl group. Suitable alkyl orthosilicates are the lower alkyl orthosilicates such as butyl silicate, propyl silicate, ethyl silicate and methyl silicate. Ethyl silicate is preferred as it is readily available, is the most common and is easily handled. The lower alkyl orthosilicates other than ethyl orthosilicate are generally not preferred for other reasons such as expense or toxicity. For example, methyl silicate is quite toxic, particularly to the human cornea, and therefore is rather difiicult to handle. The orthosilicate is incorporated into the solid catalyst in an amount from about 1% to 8% by weight and preferably between about 2% to 6% by weight.

The treatment or incorporation of the catalyst with the alkyl silicate compound may be applied at various stages in the preparation of the catalyst, but is preferably ap plied to the support prior to incorporation of the dehydrogenation component. Incorporation of the silicate on the catalyst can be accomplished by absorption, impregnation, soaking or the like. The silicate is preferably diluted with a suitable non-aqueous solvent such as cyclohexane, benzene, pentane, isopentane and the like. Where the solid support is absorptive, it may be mixed or slurried with the solution containing the alkyl silicate for a suffi cient length of time until the silicate has been absorbed from the solvent, the solvent then being removed and the remaining solid dried. Where the solid support is rather non-absorptive, the solvent should be relatively volatile compared to the alkyl silicate so that the solvent can be readily evaporated, leaving the silicate on the support. Non-aqueous solvents are necessary since the alkyl silicates are readily hydrolyzed with water to form the respective alkyl alcohols and silicic acid. Thecatalyst support may be any of the supports conventionally used for reforming catalysts such as alumina or silica. Such carriers catalysts are usually promoted with from about 0.1 to

by weight and preferably 0.1 to 3% by weight of a halogen. Chlorine and fluorine or mixtures thereof are normally used and are generally present in a concentration less than 1% by weight. The halogen supplies an acidic site which functions catalytically in various of the reforming reactions.

The catalyst contains from about 0.1 to 2.0% by weight and preferably 0.25% to 1% by weight of platinurn which is the main dehydrogenation promoter associated with the acidic support. Platinum may, however, be substituted in whole or in part by other platinum group metals such as Ru, Rh, Pd, Os and Ir.

The present improved catalysts are applicable to the catalytic reforming of conventional reforming feeds as discussed above. The feed preferably contains less about 5 parts per million of water, less than 100 parts per million of sulfur and less than 25 parts per million of nitrogen. The catalyst may be used in the form of a fluidized bed, a moving bed of particles or a fixed bed of particles.

The invention will be illustrated by the following examples:

Example 1 Several reforming catalysts were prepared with and without treatment with alltyl silicate for testing in the reforming process. The support was a high surface area silica having a surface area of 765 square meters per gram, a pore volume of 0.55 ccs. per gram and containing 0.55% by weight alumina. The silica was pelleted and then ground to a particle size of 912 mesh. To 41.9 grams of the silica was added 1.76 grams of tetraethyl orthosilicate dissolved in about 75 ccs. of cyclohexane. The mixture was allowed to stand untfl the refractive index of the supernatant liquid was substantially that of cyclohexane, after which the solids were filtered from the solution and dried for about 15 hours at 150 C. The dried silica was then impregnated with chloroplatinic acid to provide 0.5% by weight platinum in the final catalyst. The impregnated material was dried at 150 C. for approximately 4 hours after which it was acidified by an aqueous solution of hydrofluoric acid to provide a final catalyst containing 1% fluorine. The impregnated and acidified catalyst was dried at 150 C. and then heated to approximately 450 C. in an atmosphere of hydrogen to reduce the platinum. A similar catalyst was prepared from the untreated silica gel.

The treated and untreated catalysts were then used to reform a desulfurized naphtha fraction predominantly of C7 to C hydrocarbons and boiling in the range of about 200 F. to 390 F. Product yield and octane are given in Table I for reforming at 475 C., 250 pounds p.s.i.g., hydrogen/ oil mol ratio of 5 and a liquid hourly space velocity of 4.

TABLE I Efiect of Ethyl Ortlzosilicate on Platinum Reforming Catalysts [Conditions: 475 C., 250 p.s.i.g., H2/Oil=5, 4 LHSV] Catalyst 1% 170.5% Pt/ Products, Percent vol. on feed:

4 Example 11 A portion of the 9-12 mesh silica was calcined at 600 C. for approximately 48 hours and then treated with tetraethyl orthosilicate, impregnated with platinum, and acidified according to the procedure given in Example I. This catalyst was compared with a widely used conventional reforming catalyst comprising about 0.7% platinum, 0.35% chlorine, and 0.35% fluorine on alumina for the dehydrocyclization of normal heptane. The reforming conditions were 500 C., 5 hydrogen/oil mol ratio, 250 p.s.i.g. and a varying space velocity. The r sults are indicated in Table II.

TABLE II Comparison of Reforming Catalysts for Conversion of n-Heptane [Conditions: 500 C., 5 Hz/feed, 250 p.s.i.g.]

Catalyst 1% F/O.5% Pt/4% 03575170357 (ll/0.7

(EtO);Sl/Sl0z lt/Al O;

WHSV 10 5 2. 5 10 5 2. 5 Conversion percent mo1 55 82 45 66 84 Tolune Formed mole/ mols n-C HH Feed 12 18 19 9 15 18 a To products other than iso and normal heptsne.

Example Ill TABLE III Reforming Temperature and Product Yield at 100 F10 C Reformate Catalyst 1% F/0.5% Pt/4% 0.35% F/0.35% Cl/ (ElZO)4Si/S10g 0.7% Pt/Al O;

Temperature 480 507 Yiell, percent v. of feed:

The higher activity of the treated catalyst is indicated by the considerably lower temperature required, i.e. 27 C. The improved yield is indicated in the higher volume of C reformate obtained with the reduction in loss to gas.

Example IV Additional catalysts were prepared according to the method described in Example I except that the tetraethyl orthosilicate incorporated in the catalyst was varied in amount. These catalysts were then tested at the same reforming conditions and the same feed as in Example I. The results are given below in Table IV.

TABLE IV Efiect of T etraethyl Ortlzosilicate on Reforming Yield Percent w. (EtOhSi in Catalyst 2 4 6 Example V A widely used commercial reforming catalyst comprising, by weight, 0.75% platinum, 0.35% fluorine, and 0.35 chlorine on alumina was tested for activity, with Catalyst I Untreated Treated Temperature, 475 500 475 500 00+ Octane No., F10 96. 3 102. 9 98.6 104. e

I claim as my invention:

1. In a process for the catalytic reforming of a hydrocarbon oil, the improvement which comprises contacting the hydrocarbon oil under reforming conditions with a solid catalyst comprising a minor amount of a platinum group metal and 0.1% to about by weight halogen supported on a gel as carrier and on which has been incorporated from about 1% to about 8% by weight of tetraethyl orthosilicate, said gel being selected from the group consisting of silica, alumina, and mixtures thereof.

2. In a process for the catalytic reforming of a hydrocarbon oil, the improvement which comprises contacting the hydrocarbon oil under reforming conditions with a solid catalyst comprising 0.1% to about 2% by weight of platinum and 0.1% to about 5% by weight halogen supported on a gel as carrier and on which has been incorporated from about 1% to about 8% by weight of tetraethyl orthosilicate, said gel being selected from the group consisting of silica, alumina, and mixtures thereof.

3. In a process for the catalytic reforming of a hydrocarbon oil, the improvement which comprises contacting the hydrocarbon oil under reforming conditions with a solid catalyst comprising 0.1% to about 2% by weight platinum and 0.1% to about 5% by weight halogen sup ported on silica gel and on which has been incorporated from about 2% to about 6% by weight tetraethyl orthosilicate.

4. The process according to claim 3 wherein the halogen is a mixture of fluorine and chlorine.

5. The process according to claim 3 wherein the halo- 4 gen is fluorine.

6. The process according to claim 3 wherein the halogen is chlorine.

7. In a process for the catalytic reforming of a hydrocarbon oil, the improvement which comprises contacting the hydrocarbon oil under reforming conditions with a solid catalyst comprising 0.1% to about 2% by weight platinum and 0.1% to about 5% by weight halogen supported on alumina and on which has been incorporated from about 2% to about 6% tetraethyl orthosilicate.

8. The process according to claim 7 wherein the halogen is a mixture of fluorine and chlorine.

9. The process according to claim 7 wherein the halogen is fluorine.

10. The process according to claim 7 wherein the halogen is chlorine.

11. A catalyst having activity for the reforming of hydrocarbon oil prepared by treating an activated gel support selected from the group consisting of silica, alumina, and mixtures thereof with a non-aqueous solution of tetraethyl orthosilicate in an amount to incorporate thereon from about 1% to about 8% by weight of said orthosilicate, and impregnating the treated support with from about 0.1% to about 2% by weight of a platinum group metal and from 0.1% to about 5% by weight of halogen.

13. The catalyst according to claim 11 wherein the gel is alumina, the impregnated metal is platinum, and the halogen is a mixture of chlorine and fluorine.

13. The catalyst according to claim 12 wherein the halogen is chlorine.

14. The catalyst according to claim 12 wherein the halogen is fluorine. V

15. The catalyst according to claim 11 wherein the gel is silica, the impregnated metal is platinum, and the halogen is a mixture of chlorine and fluorine.

16. The catalyst according to claim 15 wherein the halogen is chlorine.

17. The catalyst according to claim 15 wherein the halogen is fluorine.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR THE CATALYTIC REFORMING OF A HYDROCARBON OIL, THE IMPROVEMENT WHICH COMPRISES CONTACTING THE HYDROCARBON OIL UNDER REFORMING CONDITIONS WITH A SOLID CATALYST COMPRISING A MINOR AMOUNT OF A PLATINUM GROUP METAL AND 0.1% TO ABOUT 5% BY WEIGHT HALOGEN SUPPORTED ON A GEL AS CARRIER AND ON WHICH HAS BEEN INCORPORATED FROM ABOUT 1% TO ABOUT 8% BY WEIGHT OF TETRAETHYL ORTHOSILICATE, SAID GEL BEING SELECTED FROM THE GROUP CONSISTING OF SILICA, ALUMINA, AND MIXTURES THEREOF 